How Germs Can Ruin Your Smile

A trip to the dentist is for many a stressful event, especially when accompanied by the dreaded words: "You have a cavity." The news can be both a personal and financial nightmare as future visits must be scheduled for the sometimes painful and expensive remedial action. It's a natural part of life for many and unfortunately, there seems to be little that can be done.

Naturally, you can blame germs for this aggravation.

The main cause is a group of bacteria known for their ability to grow on hard surfaces, such as the enamel of the teeth, and slowly soften the matrix through the use of acids. The most common culprit is Streptococcus mutans.

The bacterium uses sugars to form lactic acid and a solid sugar byproduct, known as glucan, which helps the intruder hide from the mouth's cleaning and repairing tool, saliva. The lactic acid slowly breaks down the enamel and eventually forms a cavity. Other forms of these bacteria include the appropriately named Porphyromonas gingivalis, Actinomyces viscocus and the sister strain to S. mutans, Streptococcus sobrinus (literally Latin for sister).

The common belief is that these bacteria have caused us to gnash our teeth since the dawn of humankind. Yet a study released this past week from of the Australian Centre for Ancient DNA at The University of Adelaide in Australia suggests that this may not be the case.

In the paper, the team looked at 34 skeletal remains ranging in age from 400 to 7,500 years and investigated the microbiome of the dental plaque. They divided the nature of the subjects into categories based on the era they lived, including the Mesolithic Period, the Neolithic Period, the Bronze Age, Medieval Times and finally modern day.

The researchers had expected to see some differences in the microbial makeup of the mouth over time and they were not disappointed. For example, farmers from today had few differences than those from 7,500 years ago.

But there was one finding that took them by surprise. For some reason, that cavity causer, S. mutans, could not be found in samples prior to the Bronze Age. A closer look at the microbiome showed that the actual diversity of bacteria in the mouth dropped as time progressed. In essence, the mouth became less germy, yet there was a greater chance for disease.

The authors suggested that the cause for this appearance and increase in S. mutans and other pathogenic bacteria was the dawn of food processing, which saw the use of refined sugars and grains and the reduction of the overall diversity of nutrients. The bacteria would find a home in these sugar-rich products and eventually colonize and start to degrade tooth enamel.

The premise makes perfect sense as there has been a longtime belief that the change in our overall diet has led to an increase in oral diseases as well as many other chronic problems .

But one doesn't need to have a historical perspective to realize this loss of diversity. Recent analyses of the oral microbiological ecology of women and children have revealed that there is a reduction in diversity with increased risk for cavities. A diet that is filled with sugar is almost always going to lead to the growth of harmful bacteria and a reduction or elimination of those that are helpful.

Thankfully, while our ancestors had to rely on sticks and leaves to keep their mouths fresh, we have an entire industry devoted to the maintenance of our oral health. We have toothbrushes, toothpaste, dental floss, and other creative oral health ideas all designed to help us cope with the fact that our diets have become as pathogenic to our teeth as the bacteria that cause the cavities. Yet while we may spend hundreds if not thousands of dollars to keep our teeth white and shining, there may be a better and more natural option to help our teeth survive: force the bad germs to compete with the good.

Back in 1981, a group out of the Department of Microbiology and Institute of Dental Research at the University of Alabama in Birmingham published a study that showed the bacterium Lactobacillus casei could somehow stop the effects of S. mutans in the mouth and even help to prevent cavities.

The study was somewhat odd as lactobacilli, which turn sugars into that enamel eating lactic acid, were considered to be harmful. But this study suggested that perhaps some of these lactobacilli were more capable of using the sugars in the mouth without causing injury and at the same time, keeping the bad bacteria at bay.

The work was barely noticed by most but some researchers did follow up and eventually found that certain lactobacilli could indeed help to keep the mouth healthy. Not surprisingly, these same bacteria, including Lactobacillus rhamnosus, Lactobacillus acidophilus and Lactobacillus fermentum, were all found to help the mouth fight off dental problems. If any of these names sound familiar, it's because they are also collectively better known as probiotics. At the moment, the jury is still out on whether probiotic-containing foods such as yogurts and fermented foods can ultimately prevent cavities but there is hope that a modification of the diet to include these helpful bacteria could eventually lead to a better smile.

Ultimately, there is no way to prevent the necessary visit to the dentist as oral health is paramount. However, over the coming years, there may be novel ways - both medically and naturally - to help our teeth in between those visits. Perhaps one day, we may no longer need to fear the dreaded cavity conundrum and instead, sit back, relax and welcome the words we all love to hear...